But a double from Steven Thompson and a Nigel Hasselbaink penalty secured the SPL side's progress.

Andy Jackson scored a third for Morton with ten minutes remaining, but St Mirren held on for victory.

Morton had started the match brightly and Teale's set-piece opener had come against the run of play; St Mirren's summer signing powering the ball past a helpless Colin Stewart from 25 yards out.

We're delighted that our fans have got the bragging rights again

Danny LennonSt Mirren manager

The Greenock side bounced back 8 minutes later when MacDonald picked out Tidser inside the box, the former Celtic midfielder coolly slotting into the left hand corner.

The roles were then reversed as Tidser set up MacDonald for his fourth goal of the season, the former St Johnstone striker sending a bending ball past Craig Samson in the St Mirren goal.

Buddies' boss Danny Lennon reshuffled to a 3-5-2 formation at half time and was rewarded when Hasselbaink picked out Thompson who continuted his scoring run with 54th minute strike

Hasselbaink then drew Stuart McCaffrey into a tackle in the box for which referee Calum Murray awarded a penalty: the Dutchman slotting home a right-footed shot to restablish Saints' lead.

The tie looked to have been put beyond Morton's reach in the 65th minute when Jeroen Tesselaar set up a close range header for Thompson, the striker rising in the box for his fourth goal of the season.

Morton introduced substitute Jackson, who had an immediate impact, pulling one back for Morton after being set up by Ross Forsyth.

St Mirren then switched to a five man defence, and survived a flurry of late chances.

There had been a concern for the Paisley club when the influential Hasselbaink had to be replaced after 68 minutes on his return from suspension.

But St Mirren manager Danny Lennon played down what appeared to be a hamstring injury after the match.

"He was complaining of a wee pull, but he seems fine now. It was probably toothache he had," Lennon told BBC Radio Scotland.

"I thoroughly enjoyed the game.

"It wasn't as pleasing on the eye as some of the football we've played this season and I have to give Allan Moore and Morton credit for that.

"We're delighted that our fans have got the bragging rights again."

Meanwhile, Morton boss Allan Moore felt poor refereeing decisions may have cost his side the match.

"I thought a couple of decisions that went against us cost us goals," he said.

"The first one the boys is two yards away and he gives a free-kick (for handball). I don't know if it was a penalty, it was a bit dubious."